Prior art industrial luminaires of the type depicted in FIG. 1 and designated by reference numeral 10, for example, have proven unsatisfactory for use in commercial food processing and related operations which require regular cleansing or sterilization of the factory premises, including its machinery and lighting units. These prior art industrial luminaire designs have typically incorporated ballast housings 12 and optical units or lenses 14 which have numerous external components having horizontal or near horizontal surfaces 16. Because of their exposure to the surrounding atmosphere, these component surfaces are particularly susceptible to the accumulation of contaminants such as food stuffs and the like. As appreciated by those skilled in the art, such accumulation may enhance the growth of bacteria and other microscopic organisms, none of which are desirable from an operations standpoint.
In an effort to overcome the above-identified limitations of the prior art, Applicants sought to design and develop an improved luminaire assembly having reduced external components and horizontal surfaces. As a starting point for their design work, Applicants thus turned their attention toward the design of a luminaire assembly having an optical assembly with a three-dimensional shape which enhanced the shedding of food particles and promoted the desired objective of easy cleanability. Keeping in mind the desired application, i.e. food processing operations which require regular cleansing, the optical assembly was also required to be affixed in a sealed relationship with a ballast housing in a substantially water-tight relationship so as to enclose and protect an internal lamp. As appreciated by those skilled in the art, this latter sealing requirement led to the further requirement of a breathing mechanism so as to provide proper ventilation for the enclosed lamp. Such a mechanism is especially required when using High Intensity Discharge (HID) lamps as anticipated for use with the present invention and, which are known to produce extreme heat during operation.
Previous attempts have been made to incorporate ventilation and heat dissipation means within industrial luminaires. These prior art attempts, however, have failed to meet the objectives addressed by Applicants and resolved by the invention disclosed herein because these prior art devices have inherently introduced additional external components which are prone to accumulation of contaminants. Examples of these prior art luminaires which have incorporated one or more ventilation means are shown, for example, in U.S. Pat. Nos. 5,174,646, 5,134,554, 5,138,541, 3,521,701 and 4,704,665 issued to Siminovitch et al, Donato et al, Kano, Shinjiro Mori, and Grindle, respectively.
U.S. Pat. No. 5,174,646 issued to Siminovitch et al discloses a lighting fixture which includes a heat transfer structure which is independent of and disposed externally of the housing for transferring heat energy generated from a fluorescent lightbulb through the heat transfer structure to the outside of the housing.
Similarly, U.S. Pat. No. 5,134,554, issued to Donato, discloses a lighting system which incorporates a plurality of air-flow channels between the globe support housing and the lamp socket support body. As shown and disclosed, air-flow passageways are provided in communication with the air-flow channels. The air-flow passageways as well as the air-flow channels are further provided in communication with the ambient atmosphere. In operation, air flow patterns created by the air-flow passageways and channels of the luminaire assembly serve to carry heat away from the halogen lamp up along the air-flow channels and into the ambient atmosphere.
U.S. Pat. No. 5,138,541, issued to Kano, is similarly directed to a refrigerator light which incorporates openings to provide effective air circulation for the lamp. As disclosed by Kano, these openings are arranged in the edge region of the lamp near the cylindrical housing outer wall such that air may enter the interior of the housing at the outside of the cold-light reflector near the outer housing wall, flow over the housing wall and then emerge from the interior of the housing in the rear region of the lamp.
U.S. Pat. No. 3,521,701, issued to Shinjiro Mori, is directed to an industrial safety illuminating apparatus which incorporates air-passageways to serve as a radiator device. As disclosed, the air-passageways are in the form of radiator pipes which extend radially on the external peripheral wall face of the unit.
Finally, U.S. Pat. No. 4,704,665, issued to Grindle, discloses an electrical luminaire comprised of weather and corrosion resistant housing material. No ventilation or breathing mechanism, however, is taught or suggested for use in connection with the invention disclosed therein.
Keeping in mind the intended application the luminaire under design, i.e., food processing and related operations, Applicants were further required to develop a luminaire assembly which, in addition to the above limitations of three-dimensional shape and thermal breathability, provided sufficient uplight and downlight capability.
Consequently, applicants recognized and addressed the need for an improved luminaire assembly which is adapted for use in food processing operations and the like which require reduced external components and horizontal surfaces so as to promote easy cleanability. Applicants further recognized and addressed the need for such an industrial luminaire having sufficient uplight and downlight capability for use in commercial food processing operations and which further permits easy relamping through an external releasable door.
Still further, applicants recognized and addressed the need for an improved luminaire assembly having the above characteristics and which further incorporates a novel breathing mechanism for providing sufficient ventilation so as to optimize the thermal operating characteristics of the luminaire thus minimizing operating costs and maximize luminaire life.